1. Field of the Invention
The present invention relates to a fan unit including a plurality of axial fans connected in series.
2. Description of the Related Art
Cooling fans are used for cooling electronic parts inside a casing of various electronic devices. The cooling fans are required to have improved air flow characteristics, i.e., an improved static pressure vs. flow rate curve with the increase in the amount of heat generation associated with performance improvement of the electronic parts and the increase in the density of the electronic parts associated with size reduction of the casing. As an exemplary cooling fan which can provide a sufficient static pressure and a sufficient flow rate, a serial axial fan unit is currently used which includes a plurality of axial fans connected in series.
The serial axial fan unit, which is typified by a counter-rotating type, can provide a high static pressure and flow rate. However, operation sounds of the axial fans may interfere with each other, causing a large or harsh noise.